Small electrical appliances are often battery powered. As batteries in such appliances exhaust their charge, they are typically replaced or recharged. Illustrative battery-powered appliances include, for example, cordless or cellular telephones. The batteries in such telephones are typically contained in a battery pack. Though usually rechargeable, such batteries may lose their ability to hold a charge and therefore require replacement. To simplify battery replacement, the battery pack is typically detachably coupled to the telephone by a fastening mechanism. Several examples of prior art fasteners are described below in conjunction with FIGS. 1a and 1b.
FIG. 1a depicts a conventional movable tab 106 for coupling a battery pack to a portable appliance such as a telephone. Movable tab 106 is formed in side 102 of battery-pack cover 100. Fixed end 108 of movable tab 106 is disposed proximal to upper edge 104 of side 102. Catch 114 protrudes from outer surface 110 of movable tab 106 near free edge 112. Pushing on outer surface 110 of movable tab 106 releases catch 114 from a notch (not shown) in the body of the telephone. The battery pack (contained within cover 100, but not shown) is then slid or pulled from the telephone for removal. The battery pack may be reinstalled by pushing or sliding toward the notch in the phone body.
Movable tab 106 of the prior art has several drawbacks, as follows. To disengage battery-pack cover 100, a force is applied to outer surface 110 of movable tab 106 above catch 114 (i.e., between catch 114 and edge 104). The disengaging force is necessarily applied to first region 109 above catch 114, since second region 111 of movable tab 106 below catch 114 is inaccessible while the battery-pack cover is engaged to the telephone. First region 109 provides a relatively short lever arm; a relatively large disengaging force is therefore required to detach the battery pack. Moreover, movable tab 106 is prone to breakage, because, as the movable tab is deflected, stresses develop therein and concentrate near where the movable tab is fixed to the cover. Excessive deflection may cause permanent deformation or fracturing of movable tab 106. If the movable tab is made thicker to improve robustness, then, undesirably, a greater force must be applied to disengage the battery pack.
FIG. 1b depicts a conventional movable tab 206 for coupling a battery pack to an appliance, such as a telephone. Movable tab 206 has fixed end 208 that depends from side 202 of cover 200 proximal to lower edge 204. Catch 214 protrudes from outer surface 210 of movable tab 206 near free edge 212. Pushing on outer surface 210 of movable tab 206 above catch 214 releases the catch from a notch (not shown) in the body of the telephone (not shown). Several drawbacks are associated with movable tab 206. In particular, like tab 106, movable tab 206 is prone to failure due to stress concentration at fixed end 208. Furthermore, tab 206 is likely to fail if it is pulled away from cover 200. In addition, foreign objects can lodge in the region between movable tab 206 and cover 200 preventing release of the cover.
In a third prior art catch (not shown), the "fixed" end of the movable tab is hingeably attached to the bottom of the battery-pack cover. A spring is typically positioned between the movable tab and a brace member to provide a biasing force for disengagement/engagement operations. Using such a spring disadvantageously increases parts count, which typically results in an increase in device cost and complexity.
As such, a need exists for a robust, inexpensive and simple to manufacture fastener for detachably coupling a battery pack or other removable part i;o a small appliance. Moreover, such a fastener should be easy for a consumer to operate and result in an aesthetic package.